1. Field of the Invention
The present invention relates to a universal guide device that is used in sliding portions of various machine tools, part-conveying systems, and so on and is capable of guiding a movable object or material over a conveyance path containing both straight and curved regions.
2. Related Art
For example, on a product line or the like in a plant, if all processing stations are arranged linearly, then no problems will take place. However, depending on the space of the plant in which a machine is installed or on the contents of the processing performed in processing stations, it may be necessary to change the direction of conveyance of materials to be processed between two adjacent processing stations. In this case, it is customary to use a pallet changer or the like to achieve a change in the direction of conveyance. Unfortunately, additional space and cost for installing the pallet changer or the like are necessary.
Known means for modifying the direction of conveyance of materials or objects without using a pallet changer include universal guide devices (as described in Laid-open, unexamined Japanese patent application Nos. 293319/1988 and 50333/1994) capable of guiding materials continuously along a path including both straight and curved lines and curved guide devices (as described in Laid-open, unexamined Japanese patent application No. 186028/1988) capable of guiding materials continuously along an annular path.
These universal guide devices and curved guide devices each comprise a track rail, a slider, and a number of balls. The rail forms longitudinally extending surfaces on which the balls roll. The slider is mounted to span the rail. Load-rolling surfaces opposite to the rolling surfaces of the rail and an endless circular path for the balls are formed on and in the slider. The endless circular path includes the load-rolling surfaces. The balls roll in the endless circular path of the slider and between the rolling surfaces of the rail and the load-rolling surfaces of the slider carry a load. The slider moves along the rail in response to rolling movement of the balls.
In the former universal guide device, each load-rolling surface of the slider is partitioned into straight load regions formed linearly and curved load regions shaped into an arc in conformity with the curvature of the rail. In each straight load region of the rail, the load acting on the slider is carried by the balls rolling in the straight load region. In each curved region, the load is carried by the balls rolling in the curved region. As a result, even if straight and curved regions are intermingled on the track rail, the slider can move along the rail through the straight and curved regions continuously.
In the latter curved guide device, the track rail is shaped into an arc having a given curvature. The load-rolling surface of the slider is shaped into an arc in conformity with the curvature of the rail. All the balls interposed between the load-rolling surface of the slider and the rolling surface of the rail roll on while carrying the load acting on the slider. In consequence, the slider can make a curved motion along the rail.
In these conventional universal guide devices and curved guide devices, the load-rolling groove or race in the slider is shaped into an arc in conformity with the curvature of the track rail to permit movement of the slider through the curved region of the rail. Therefore, it has been necessary to machine the load-rolling surface in conformity with the curvature of the rail. Consequently, it has been impossible to directly use the sliders of conventional mass-produced linear guide devices that are available in the market. Hence, the production cost is increased. Furthermore, a different slider is necessary for each different curvature of track rail. Therefore, it is laborious to machine the sliders and to manage finished products.
Where the load-rolling surface of a slider is machined into an arc, the direction of bending of the curved region of a track rail is limited to one direction, left or right. Although it is possible to transport materials and objects annularly, it is impossible to convey materials along a track including two curved regions bent in different directions such as an S-shaped track.
On the other hand, in a path between two adjacent machining stations on a product line, if materials can be transported, no problems take place. It is considered that capability to carry very large loads is not necessary in curved regions of the rail. However, during a machining process, a machining force acting on a material needs to be sustained reliably by a guide device. Straight regions of the rail are required to have ability to carry a larger load than curved regions. In the aforementioned conventional universal guide device, the load-rolling surface formed on the slider is divided into straight and curved load regions. Therefore, the straight regions of the rail have decreased ability to sustain loads. Consequently, a machining force acting on materials cannot be sufficiently sustained.
Where materials are actually transported using such universal guide devices, it is necessary to construct a moving table device from two or more universal guide devices in order to transport such materials stably. In particular, two track rails are placed parallel to each other. Plural sliders are mounted to each track rail. A table is mounted so as to span all of these sliders. The materials to be transported are placed on this table.
Where the table is moved only through a linear region or only through a curved region, if all the sliders are mounted directly to the table, no problems take place. The table can be smoothly moved. However, where the table is moved from a curved region to a straight region or vice versa continuously, if all the sliders are directly mounted to the same table, the configuration of one slider relative to the track rail is restricted by other sliders. This makes it difficult to move the table smoothly. Accordingly, where plural universal guide devices of the construction described above are used to construct the moving table device, it has been impossible to mount the sliders directly to the table.
In view of the foregoing problem, the present invention has been made. It is an object of the present invention to provide a universal guide device which can directly use sliders heretofore employed in linear guide devices and which do not need different sliders for each different radius of track rail and thus can be fabricated at lower cost than conventionally.
It is another object of the invention to provide a universal guide device in which sliders can move through two curved regions of a track rail continuously along the rail even if the two curved regions are bent in different directions and in which the sliders can move from a straight region to a curved region or vice versa continuously without sacrificing the ability of the rail to sustain a load in the straight region even if the rail contains both straight and curved regions.
It is a further object of the invention to provide a moving table device comprising plural parallel track rails and plural sliders mounted to each track rail, the moving table device being characterized in that smooth movement of the sliders is assured even if a table is supported by the sliders that are four or more in number.
To achieve the objects described above, a universal guide device in accordance with the present invention comprises: a track rail including a straight region and a curved region shaped into an arc with a given radius of curvature and having ball-rolling surfaces on both its side surfaces, the ball-rolling surfaces extending longitudinally; a slider having a saddlelike cross section and mounted to span the track rail; load-rolling surfaces formed on the slider and located opposite to the rolling surfaces, respectively, of the rail; and an endless circular path for a number of balls. The circular path is formed on the slider and includes the load-rolling surfaces. The numerous balls sustain a load between each rolling surface of the track rail and each load-rolling surface of the slider. The load-rolling surfaces formed on the slider are formed linearly. The width of the curved region of the track rail is set narrower than the straight region of the rail.
In this universal guide device in accordance with the present invention, the load-rolling surfaces formed on the slider are not shaped into an arc corresponding to the curvature of the curved region of the track rail. Rather, the load-rolling surfaces are formed linearly in conformity with the rolling surfaces of the straight region of the track rail. In the present invention, however, the curved region of the rail is set narrower than the straight region of the rail. Therefore, if the rolling surfaces of the rail assume the form of an arc, and if the load-rolling surfaces of the slider are linear, the slider can engage the curved region of the rail and can move along the curved region without trouble.
When the slider is moving through the curved region of the track rail, the balls are squeezed in between the arc-shaped rolling surfaces formed longitudinally of the rail and the linear load-rolling surfaces formed on the slider and roll along the load-rolling surfaces while carrying the load. Therefore, with respect to the numerous balls rolling on the load-rolling surfaces, only some of the balls carry the load between the rolling surfaces of the rail and the load-rolling surfaces of the slider.
In this universal guide device in accordance with the present invention, the load-rolling surfaces formed on the slider are shaped linearly rather than into an arc. Therefore, the sliders of linear guide devices can be used intact. Furthermore, an operation for machining the load-rolling surface into an arc in conformity with the curvature of the track rail is dispensed with. Therefore, it is possible to fabricate a universal guide device at quite low cost. Furthermore, the linearly formed load-rolling surfaces have no directivity. Consequently, even if two curved regions bent in different directions are contained in the rail, the slider can move through these curved regions continuously.
In addition, in the universal guide device in accordance with the present invention as described above, all the balls rolling on the load-rolling surfaces of the slider bear against the rolling surfaces of the track rail within the straight region of the rail. Therefore, the ability of the slider to sustain a load is not impaired, unlike the case in which only some balls bear against the rolling surfaces in a curved region. If large loads act on the slider, the loads can be sufficiently sustained.
In the present invention, as long as the ball-rolling surfaces on the track rail side are formed on the surfaces of the rail, balls forming a row and rolling on the load-rolling surface of the slider do not simultaneously touch the arc-shaped rolling surface on the rail side. Therefore, this rolling surface may be shaped in the same way as the rolling surface of the prior art curved guide device without needing any special machining operation. Furthermore, this track rail can be easily fabricated, because one surface of the rail and the arc-shaped rolling surface formed on it can be simultaneously ground. However, where an upward facing rolling surface is formed on the top surface of a track rail, this rolling surface needs to be machined in a special manner. In particular, a downward facing load-rolling surface is linearly formed on the slider in an opposite orientation to the upward facing rolling surface of the track rail. Consequently, this upward facing rolling surface needs to have such a width that balls forming a row and rolling on the downward facing rolling surface of the slider simultaneously touch the upward facing surface.
In the universal guide device in accordance with the present invention, the slider can move through both straight and curved regions of the track rail freely. Therefore, if this rail is composed of only curved regions, the slider can move along th e annular rail. That is, where attention is paid to only the curved region of the rail, the universal guide device in accordance with the invention can be regarded as a curved guide device.
As mentioned previously, in the universal guide device in accordance with th e present invention, the straight and curved regions of the track rail differ in width. Therefore, it is desired to provide an intermediate rail portion connecting the straight and curved regions of the rail such that the width of the rail varies continuously in this intermediate rail portion.
Moreover, a moving table device can be built using universal guide devices of the construction in accordance with the invention as described above. Specifically, plural track rails are mounted parallel to each other on a fixed portion such as a pedestal or a base. A table is mounted to span sliders that move on these rails. However, if two or more sliders are mounted to each rail, and if all of the sliders are directly mounted to the same table, it will be difficult to move the table smoothly between the straight and curved regions of the rail, as mentioned previously.
In view of this, first and second track rails are mounted parallel to each other. Plural sliders are mounted to each of these rails. A fixed plate is made to span one slider mounted to the first rail and one slider mounted to the second rail such that these two sliders are coupled. Another fixed plate is bridged across another slider mounted to the first rail and another slider mounted to the second rail, and so on. Preferably, the table is mounted so as to be rotatable relative to the fixed plates. Where the moving table device is constructed in this way, even if the table is supported by the sliders that are four in number, the first fixed plate bridged over the first row of sliders that is the forerunner in the direction of movement and the second fixed plate bridged over the second row of sliders rotate in such a way that the sliders are oriented in the tangential direction of the rails. The distance between the sliders on the rails is made variable. Hence, the sliders can move smoothly.
Additionally, the table can be smoothly moved between the straight and curved regions of the rail by mounting the first and second rails parallel to each other, mounting plural sliders to each of the rails, and mounting the table so as to be rotatable relative to the sliders. That is, in this structure, when the sliders move through the curved region of the rail, they rotate to arbitrary directions so as to orient themselves to the tangential direction of the rails. This permits smooth movement of the sliders.
As described thus far, in the universal guide device in accordance with the present invention, the load-rolling surfaces formed on the sliders are only required to be shaped linearly rather than into an arc. Therefore, the sliders of numerous linear guide devices available on the market can be used intact. Moreover, it is not necessary to machine the load-rolling surfaces in conformity with the curvature of the rails. In consequence, the sliders can be manufactured easily and inexpensively.
Since the load-rolling surfaces formed on the sliders have no directivity, if each track rail has two curved regions bent in different directions, the sliders can move through the curved regions continuously along the rail. For example, materials can be guided freely along a track having a high degree of freedom (e.g., consisting of a combination of straight lines and curved lines such as an S-shaped track).
Because the load-rolling surfaces formed on the sliders are linear, all the balls rolling on the load-rolling surfaces of the sliders bear against the rail in the straight regions and sustain the load. Therefore, the sliders can exhibit sufficient ability to sustain the load within these straight regions. If straight and curved lines are intermingled on the rail, the sliders can move through the straight and curved regions continuously without sacrificing the ability of the rail in the straight regions to sustain the load.
Other objects and features of the invention will appear in the course of the description thereof, which follows.